SwinnyGG: "You could also turn the whole arrangement 90 degrees, if it makes it easier for you to package."
I kept dismissing this on the basis that it created more problems than it solved -- and it does if I distribute the cage equally around the balls -- but the notion struck that I don't...
SwinnyGG:" Do you know you're going to maintain the gear tooth relationships under full power? With the perimeter shell being thin, I was thinking warping of that shell might be an issue."
Everything is a trade-off. I can increase the thickness of the rim to allow the use of bigger teeth, but...
SwinnyGG: "you don't need the bearing cage to retain the balls. All it has to do is keep them evenly spaced."
If the cage is not centred by the balls, then in addition to the friction from the small areas of contact between balls within the cage holes;
you also have full circumference drag...
SwinneyGG: " Ultimately I think you're going to have problems if you're using the gear teeth for radial location and transmitting power at the same time;"
That doesn't happen. The rotor is located radially by the bearing surfaces above and below the gearteeth (as arrowed in this two-plane...
SwinnyGG:"Yep. That was pretty easy, no?"
I guess you only read half of the post to which you responded. (My bad! I hit post instead of preview before it was complete.)
Please re-read it and see why it doesn't work unless you have production facilities.
SwinnyGG: "Your concept for providing drive power has problems of its own, but you've made it abundantly clear that you came here for us to solve this one problem for you, and don't want feedback on anything else. So, I'll keep my thoughts to myself. "
No need to be coy!
First off. If the gear...
SwinnyGG: "None of us are going to spend an hour working up a detail in CAD for you,"
Why would you think that I would need you to do that? Have I not shown myself perfectly able to produce my own CAD in response to eevry question?
SwinnyGG: "The one thing you need, as far as I can tell, is a...
If you have yet to understand the question, why suggest you have an "easy answer" and then withhold even a hint to it.
No one asked for fully worked solutions; just ideas.
Which I will once again summarise as: How to support this rotor (~128.5g), whilst it spins on its own axis at 2000-3000...
I'm a 65 y/o with 45+ years of engineering experience taking remote study courses for my own edification.
I could only register here as a "student"; as I do not have a 'company name' to satisfy any other category.
(I almost never did; I was a self employed consultant for the last 34 years of my...
SwinnyGG: "Welcome to designing things. Of all the problems you've asked questions about this is probably the easiest one."
So easy you've decided to keep the answer -- to the ONLY question I have asked -- as an exercise for the reader. Thanks a bunch.
3DdDave:"There's not a lot of extra friction from spacers, which is why they are used. "
The problem with a traditional cage spacing arrangement,
is where do you put it?
Purple is the rotor; blue the body in which it rotates, yellow the flange that retains the upper bearings:
An...
3DDave:""How fast will THOSE be rotating?"
Sorry, misunderstood you.
As drawn, the gear ratio is 7.5:1, so the 5x16x5 bearings would be doing circa 20,000 rpm.
As open bearings they are good to 43000rpm; or 36000 with seals.
SwinnyGG:"Are you trying to build a drone using this arrangement instead of normal shaft driven rotors?"
I specifically do not want to get into the overall project. The design is coming along nicely, and isn't open to change.
If you'd like to see some stuff about a related design (not mine)...
3DDave:"So, how fast will those be rotating? "
2000-3000rpm (as in OP)
3DDave:"Don't use steel or use fewer with a generous separator. There are other ball bearing materials."
I've looked at Delrin balls, which is 1/7th weight; but about 10x the price :(
Using spacers is problematic because...
3DDave:"Why not include the inner race as part of the rotor and create your own outer race? Pack in some ball bearings; the loads for that size are very low; 6-8 mm balls will be more than enough."
If I went for a full compliment ~66 per race, of 6mm steel balls, it would weight roughly 0.25kg...
GregLocock:"How about an air bearing?"
The rotor is to be 3D printed (UV resin mLCD), which has a basic pixel size of 0.05mm. Air bearings require much finer detail.
Greg Locock:"New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies...
A couple of ideas I've already had:
The pink balls are loose Delrin 3mm balls. Needs a cage or low-friction spacers of some kind.
The 3 'gear bearings' @ 120° have (say) 5x16x5 minature deep groove bearings top and bottom.
Two are fixed position, 1 spring loaded or adjustable. (1 drives the...
Here you go:
The rotor is driven via the external gear teeth.
It need to be supported by some external arrangment to bear rotation and axial forces in one direction.
Ideas?
